Devonian Trace Fossils of the Horlick Formation, Ohio Range, Antarctica: Systematic Description and Palaeoenvironmental Interpretation

Abstract

The clastic Horlick Formation contains an ichnofauna of 28 ichnotaxa dominated by burrowers. These are a mixture of simple vertical forms (Skolithos linearis, S. magnus, Bergaueria cf. langi, Rosselia socialis, Monocraterion isp.), U or arc-like forms (Diplocraterion parallelum, Arenicolites types A and B, Catenarichnus antarcticus, C. isp., aff. Lanicoidichna isp.), and complex, vertical spiral structures (Asterosoma isp., Spirophyton isp.). Horizontal burrows include Ancorichnus cf. capronus, Palaeophycus tubularis, and Psammichnites devonicus isp. nov. Surface traces comprise Haplotichnus isp., Cruziana problematica, C. rhenana, Rusophycus aff. carbonarius, R. isp., Protovirgularia rugosa, Lockeia ornata and cubichnia indet., while trackways include Diplichnites gouldi, D. isp., Maculichna? isp. and large imprints. The Horlick Formation (maximum 56 m) records an early Devonian transgression onto a deeply weathered land area that lay in the direction of Marie Byrd Land, spreading from the South Africa sector of Gondwana. Analysis of the trace fossils confirms their formation in near-shore to intertidal environments, with some ichnotaxa living close to the marine/fluvial boundary (e.g., Spirophyton, aff. Lanicoidichna, Cruziana problematica, Rusophycus aff. carbonarius, Maculichna?). The ichnofauna probably comprised a variety of marine suspension and deposit-feeding worms, shallow burrowing molluscs (bivalves and possibly bellerophontids) and several different types of arthropods, including trilobites.

Keywords:

• Trace Fossils
• Devonian
• marine
• clastic sediments
• Ohio Range
• Antarctica

ACKNOWLEDGMENTS

I gratefully acknowledge the companionship of colleagues Lucy Force, Karl Kellogg, and Graeme Ayres during the first deep-field season in the Ohio Range, and Jane Newman, Jonathon Aitchison, and Bill Atkinson during the second deep-field season three years later. I would like to thank Antarctica New Zealand (then Antarctic Division, DSIR) for their excellent support, and the Scott Base staff for their enthusiasm during the short times we were on base. I have valued the expertise and advice of fellow Antarctican, Molly Miller, during numerous email and face-to-face discussions about trace fossils. Alfred Uchman, as referee, did much to help make this a better paper by offering advice and pointing me towards some relevant publications. I also thank the unknown second referee who raised some significant points. The help of the New Zealand Advisory Committee of the Trans-Antarctic Association with financial assistance in the preparation of this paper, particularly with photographic expenses, is gratefully acknowledged.